Receiving apparatus, transmitting apparatus and transmitting/receiving system

ABSTRACT

A receiving apparatus is for selecting and receiving a radio signal in a frame structure having an information body part including at least information body and an additional part including information for receiving field intensity measurement by using a plurality of antennas. The apparatus includes a controller that measures a receiving field intensity of not a first antenna which has received the information body in a transmission period of the additional part in a current frame but a second antenna, and measures a receiving field intensity of the first antenna in a transmission period of the information body part in the current frame, and if the receiving field intensity of the second antenna exceeds the receiving field intensity of the first antenna, selects and changes to the second antenna as the first antenna of a next frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/483,355, filed Jul. 7, 2006, which is the National Stage ofInternational Application No. PCT/JP2005/000115, filed Jan. 7, 2005, andwhich claims priority from Japanese Patent Applications No. 2004-002423,filed Jan. 7, 2004; No. 2004-026875, filed Feb. 3, 2004; No.2004-061277, filed Mar. 4, 2004; No. 2004-071579, filed Mar. 12, 2004;No. 2004-071580, filed Mar. 12, 2004; and No. 2004-071581, filed Mar.12, 2004, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmitting apparatus fortransmitting an imaged video signal, a receiving apparatus for receivingthe video signal by using a plurality of antennas, and atransmitting/receiving system having the transmitting apparatus and thereceiving apparatus, and particularly to a transmitting/receiving systemfor receiving a radio video signal transmitted from a capsule endoscopewithin a subject by using a plurality of antennas outside the subject.

2. Description of the Related Art

In recent years, in the field of endoscope, there has appeared a swallowtype capsule endoscope. This capsule endoscope is provided with animaging function and a wireless communication function. The capsuleendoscope has a function of, after being swallowed from the mouth of apatient for observation (inspection), moving and sequentially imaginginside the body cavity, for example, inside the organs such as stomachand small intestine according to their peristalses before beingdischarged from a human body.

While moving inside the body cavity, image data imaged inside the humanbody by the capsule endoscope is sequentially transmitted to the outsidevia wireless communication, and is accumulated in a memory provided inan external receiving apparatus. A patient brings the receivingapparatus comprising the wireless communication function and the memoryfunction with him/her, and consequently the patient can freely act evenin the period after he/she swallowed the capsule endoscope until it isdischarged. Thereafter, a doctor or nurse can display the organs' imageson a display based on the image data accumulated in the memory, therebymaking a diagnosis.

Generally, the receiving apparatus is constituted so that a plurality ofantennas for receiving a video signal transmitted from the capsuleendoscope are distributed outside the human body and one antenna whichis less erroneously receives the video signal is selected and changedfor reception. Japanese Patent Application Laid-Open No. 2003-19111describes a receiving apparatus which performs receiving changeover of aplurality of antennas arranged outside the human body and retrieves theposition of the capsule endoscope inside the human body as a videosignal originating source based on a field intensity received by eachantenna.

SUMMARY OF THE INVENTION

A receiving apparatus according to one aspect of the present inventionis for selecting and receiving a radio signal in a frame structurehaving an information body part including at least information body andan additional part including information for receiving field intensitymeasurement by using a plurality of antennas. The apparatus includes acontroller that measures a receiving field intensity of not a firstantenna which has received the information body in a transmission periodof the additional part in a current frame but a second antenna, andmeasures a receiving field intensity of the first antenna in atransmission period of the information body part in the current frame,and if the receiving field intensity of the second antenna exceeds thereceiving field intensity of the first antenna, selects and changes tothe second antenna as the first antenna of a next frame.

A receiving apparatus according to another aspect of the presentinvention is for receiving a radio signal, transmitted from the insideof a subject, in a frame structure having a video signal part fortransmitting at least a video signal and an additional part includinginformation for receiving field intensity measurement by using aplurality of antennas provided outside the subject. The apparatusincludes a changeover unit that selects and changes over the pluralityof antennas; a field intensity measurement unit that measures areceiving field intensity of not a first antenna which has received theradio signal in a transmission period of the additional part in acurrent frame but a second antenna, and measures a receiving fieldintensity of the first antenna in a transmission period of the videosignal part in the current frame; a selection controller that, when thereceiving field intensity of the second antenna measured by the fieldintensity measurement unit exceeds the receiving field intensity of thefirst antenna, selects the second antenna as the first antenna of a nextframe; and a changeover controller that sequentially changes over andconnects an antenna other than the first antenna selected by theselection controller in a transmission period of the additional part ofthe next frame, and changes to and connects the selected first antennain a transmission period of the video signal part.

A receiving apparatus according to still another aspect of the presentinvention is for selecting and receiving a radio signal in a framestructure having an information body part including at least informationbody and an additional part including information for receiving fieldintensity measurement by using a plurality of antennas. The apparatusincludes a controller that measures receiving field intensities of morethan two antennas in the additional part in a current frame, and selectsand changes to an antenna having the largest receiving field intensityout of the more than two antennas as an antenna for receiving theinformation body part in a current frame.

A receiving apparatus according to still another aspect of the presentinvention is for selecting and receiving a radio signal in a framestructure having an information body part including at least informationbody and an additional part including information for receiving fieldintensity measurement by using a plurality of antennas. The apparatusincludes a controller that compares a first receiving field intensity ofan antenna which has received the information body in a previous framewith a second receiving field intensity being the largest receivingfield intensity out of a result of measurement of receiving fieldintensities of more than two antennas other than the antenna in theadditional part of a current frame, and selects and changes to theantenna having the larger receiving field intensity as an antenna forreceiving the information body part in the current frame.

A receiving apparatus according to still another aspect of the presentinvention is for selecting and receiving a radio signal in a framestructure having an information body part including at least informationbody and an additional part including information for receiving fieldintensity measurement by using a plurality of antennas according to eachreceiving field intensity. Part of a synchronization period of theinformation body part is set at part or all of a receiving fieldintensity measurement period of the additional part to use asynchronization signal of the synchronization period as a signal forreceiving field intensity measurement.

A receiving apparatus according to still another aspect of the presentinvention is for selecting and receiving a radio signal in a framestructure having an information body part including at least informationbody and an additional part including information for receiving fieldintensity measurement by using a plurality of antennas according to eachreceiving field intensity. Part of a synchronization period of theinformation body part is set at part or all of a receiving fieldintensity measurement period of the additional part to use asynchronization signal of the synchronization period as a signal forreceiving field intensity measurement, and the antenna for receivingfield measurement and the antenna for receiving the information bodypart are changed over in the synchronization period according to ameasurement result of a receiving field intensity to each of theplurality of antennas.

A receiving apparatus according to still another aspect of the presentinvention is for receiving a video signal transmitted as a radio signalfrom a moving transmitting apparatus by using a plurality of antennas.The receiving apparatus includes a controller that sequentially changesover each antenna in a vertical blanking period of the video signaladded with a dummy signal for receiving intensity measurement in thevertical blanking period to detect a receiving field intensity of theeach antenna, and changes to an antenna having the largest receivingfield intensity to cause the antenna to receive a video signal otherthan in the vertical blanking period.

A transmitting apparatus according to still another aspect of thepresent invention is for transmitting an imaged video signal as a radiosignal to cause a receiving apparatus having a plurality of antennas toreceive the video signal. A dummy signal for receiving field intensitymeasurement, which sequentially changes over each antenna of thereceiving apparatus to receive the video signal and detects a receivingfield intensity of each antenna, is added and transmitted in a verticalblanking period in the imaged video signal.

A transmitting/receiving system according to still another aspect of thepresent invention includes a transmitting apparatus for transmitting animaged video signal as a radio signal and a receiving apparatus forreceiving the video signal by using a plurality of antennas. Thetransmitting apparatus includes a dummy signal adder that adds andtransmits a dummy signal in a vertical blanking period in the videosignal. The receiving apparatus includes a controller that sequentiallychanges over each antenna in the vertical blanking period to detect areceiving field intensity of each antenna from the dummy signal, andchanges to an antenna having the largest receiving field intensity tocause the antenna to receive a video signal other than in the verticalblanking period.

A receiving apparatus according to still another aspect of the presentinvention is for receiving a radio signal in a frame structure having aninformation body part including at least information body as a radiosignal transmitted from a moving transmitting apparatus and anadditional part including information for synchronization by using aplurality of antennas. The receiving apparatus includes a controllerthat sequentially changes over each antenna in a blank of the radiosignal in which a dummy signal for receiving intensity measurement isadded in the blank of the information body part whose arrangementposition is previously determined to detect a receiving field intensityof each antenna, and changes to an antenna having the largest receivingfield intensity to cause the antenna to receive a radio signal of theinformation body part other than in the blank.

A transmitting apparatus according to still another aspect of thepresent invention is for transmitting an imaged video signal as a radiosignal to cause a receiving apparatus having a plurality of antennas toreceive the video signal. Each antenna of the receiving apparatus issequentially changed and received in a horizontal blanking period in thevideo signal to add and transmit a dummy signal for receiving fieldintensity measurement for detecting a receiving field intensity of eachantenna.

A transmitting/receiving system according to still another aspect of thepresent invention includes a transmitting apparatus for transmitting animaged video signal as a radio signal and a receiving apparatus forreceiving the video signal by using a plurality of antennas. Thetransmitting apparatus includes a dummy signal adder that adds andtransmits a dummy signal in a horizontal blanking period in the videosignal. The receiving apparatus includes a controller that sequentiallychanges over each antenna in the horizontal blanking period to detect areceiving field intensity of the each antenna from the dummy signal, andchanges to an antenna having the largest receiving field intensity tocause the antenna to receive a video signal other than in the horizontalblanking period.

A receiving apparatus according to still another aspect of the presentinvention is for receiving a radio signal in a frame structure having aninformation body part including at least information body as a radiosignal transmitted from a moving transmitting apparatus and anadditional part including information for receiving field intensitymeasurement. The receiving apparatus includes an antenna changeover unitthat is connected to each antenna in correspondence to arrangementpositions of the plurality of antennas and detects a connection state ofeach antenna to change over the connected antennas according to aninstruction, and a controller that sequentially changes to an antennawhose connection has been detected by the antenna changeover unit onreception of the additional part to detect a receiving field intensity,and changes to an antenna having the largest receiving field intensityto cause the antenna to receive a radio signal of the information bodypart.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the entire structure of a wirelessin-subject information acquiring system including a receiving apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a structure of the receiving apparatusshown in FIG. 1;

FIG. 3 is a block diagram showing a detailed structure of a sample holdcircuit shown in FIG. 2;

FIG. 4 is a block diagram showing a detailed structure of a changeoverswitch shown in FIG. 2;

FIG. 5 is a diagram showing a frame format of a radio signal transmittedfrom a capsule endoscope shown in FIG. 1;

FIG. 6 is a time chart showing a receiving field intensity measurementprocessing for each frame by the receiving apparatus shown in FIG. 1;

FIG. 7 is a flowchart showing an antenna changeover processing procedureby the receiving apparatus shown in FIG. 1;

FIG. 8 is a block diagram showing a structure of a receiving apparatusaccording to a second embodiment of the present invention;

FIG. 9 is a time chart showing a receiving field intensity measurementprocessing for each frame by the receiving apparatus shown in FIG. 8;

FIG. 10 is a block diagram showing a structure of a receiving apparatusaccording to a third embodiment of the present invention;

FIG. 11 is a timing chart for explaining an antenna changeoverprocessing by the receiving apparatus shown in FIG. 10;

FIG. 12 is a block diagram showing a structure of a receiving apparatusaccording to a fourth embodiment of the present invention;

FIG. 13 is a timing chart for explaining an antenna changeoverprocessing by the receiving apparatus shown in FIG. 12;

FIG. 14 is a block diagram showing a structure of a receiving apparatusaccording to a fifth embodiment of the present invention;

FIG. 15 is a diagram for explaining a frame format;

FIG. 16 is a timing chart for explaining an antenna changeoverprocessing by the receiving apparatus shown in FIG. 14;

FIG. 17 is a block diagram showing a structure of a capsule endoscopeaccording to a sixth embodiment of the present invention;

FIG. 18 is a block diagram showing a structure of a receiving apparatusaccording to the sixth embodiment of the present invention;

FIG. 19 is a diagram showing a frame format of a radio signaltransmitted from the capsule endoscope shown in FIG. 17;

FIG. 20 is a time chart showing a processing for receiving fieldintensity measurement and antenna changeover by the receiving apparatusshown in FIG. 18;

FIG. 21 is a time chart showing a variant of the processing forreceiving field intensity measurement and antenna changeover by thereceiving apparatus shown in FIG. 18;

FIG. 22 is a block diagram showing a structure of a capsule endoscope 3according to a seventh embodiment of the present invention;

FIG. 23 is a block diagram showing a structure of a receiving apparatusaccording to the seventh embodiment of the present invention;

FIG. 24 is a diagram showing a frame format of a radio signaltransmitted from the capsule endoscope shown in FIG. 22;

FIG. 25 is a time chart showing the processing for receiving fieldintensity measurement and antenna changeover by the receiving apparatusshown in FIG. 23;

FIG. 26 is a time chart showing a variant of the processing forreceiving field intensity measurement and antenna changeover by thereceiving apparatus shown in FIG. 23;

FIG. 27 is a block diagram showing a structure of a receiving apparatusaccording to an eighth embodiment of the present invention;

FIG. 28 is a diagram showing a structure of a connecting unit within achangeover switch;

FIG. 29 is a time chart showing a receiving field intensity measurementprocessing for each frame by the receiving apparatus shown in FIG. 27;

FIG. 30 is a flowchart showing an antenna changeover processingprocedure by a selection control unit of the receiving apparatus shownin FIG. 27;

FIGS. 31A and 31B are diagrams showing one example of a connectionrelationship between receiving antennas and an external device accordingto the eighth embodiment of the present invention; and

FIGS. 32A and 32B are diagrams showing one example of a connectionrelationship between receiving antennas and an external device accordingto a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A wireless in-subject information acquiring system as the best mode forcarrying out the present invention will be described below.

A wireless in-subject information acquiring system comprising areceiving apparatus according to an embodiment will be described. Thewireless in-subject information acquiring system uses a capsuleendoscope as one example of a in-subject introducing apparatus.

FIG. 1 is a schematic diagram showing the entire structure of thewireless in-subject information acquiring system. As shown in FIG. 1,the wireless in-subject information acquiring system comprises areceiving apparatus 2 having a wireless receiving function, and acapsule endoscope (in-subject introducing apparatus) 3 introduced insidea subject 1 for imaging a body cavity image and transmitting data suchas video signal to the receiving apparatus 2. Further, the wirelessin-subject information acquiring system comprises a display device 4 fordisplaying the body cavity image based on the video signal received bythe receiving apparatus 2, and a portable recording medium 5 forexchanging data between the receiving apparatus 2 and the display device4. The receiving apparatus 2 comprises a receiving jacket 2 a worn bythe subject 1, and an external device 2 b for performing a processing ofa radio signal received via the receiving jacket 2 a, or the like.

The display device 4 is directed for displaying the body cavity imageimaged by the capsule endoscope 3, and has a structure such as workstation for performing image display based on data obtained by theportable recording medium 5. Specifically, the display device 4 may beconstituted to directly display an image by a CRT display, a liquidcrystal display or the like, alternatively may be constituted to outputan image to other medium such as printer.

The portable recording medium 5 has a structure to be detachable withrespect to the external device 2 b and the display device 4 and to becapable of outputting or recording information on being mounted on theboth. Specifically, while the capsule endoscope 3 is moving inside thebody cavity of the subject 1, the portable recording medium 5 is mountedon the external device 2 b to record data transmitted from the capsuleendoscope 3. Then, after the capsule endoscope 3 is discharged from thesubject 1, that is, after the inside of the subject 1 finishes to beimaged, the portable recording medium 5 is taken out from the externaldevice 2 b to be mounted on the display device 4 so that the recordeddata is read out by the display device 4. The data exchange between theexternal device 2 b and the display device 4 is performed by theportable recording medium 5 such as compact flash (registered trademark)memory so that the subject 1 can more freely act while his/her bodycavity is being imaged than when the external device 2 b and the displaydevice 4 are wire-connected, which contributes to a reduction in timefor exchanging data with the display device 4. Here, the data exchangebetween the external device 2 b and the display device 4 uses theportable recording medium 5, but it is limited thereto, and it may beconstituted to use other recording apparatus incorporated in theexternal device 2 b to be wired- or wirelessly connected for dataexchange with the display device 4.

The receiving apparatus 2 will be described with reference to FIG. 2.The receiving apparatus 2 also has a function of receiving body cavityimage data wirelessly transmitted from the capsule endoscope 3. FIG. 2is a block diagram schematically showing the structure of the receivingapparatus 2. As shown in FIG. 2, the receiving apparatus 2 has a shapecapable of being worn by the subject 1, and comprises the receivingjacket 2 a having receiving antennas A1 to An, and the external device 2b for performing a processing for received radio signal, and the like.The respective receiving antennas A1 to An may be provided in thereceiving jacket 2 a to be directly attached to the outer surface of thesubject, or may be detachable with respect to the receiving jacket 2 a.

The external device 2 b has a function of performing a processing forradio signal transmitted from the capsule endoscope 3. Specifically, theexternal device 2 b, as shown in FIG. 2, has changeover switches SW forperforming connection changeover of the receiving antennas A1 to An, anda receiving circuit 11 connected to the rear stage of the changeoverswitches SW for amplifying and demodulating a radio signal from thereceiving antenna A1 to An changeover-connected by the changeover switchSW, and further the rear stage of the receiving circuit 11 is connectedwith a signal processing circuit 12 and a sample hold circuit 15. An A/Dconverter 16 is further connected to the rear stage of the sample holdcircuit 15. A controller C has a selection controller C1 to connect astorage unit 13, a display unit 14 and a changeover controller SCcorresponding to the signal processing circuit 12, the A/D converter 16and the portable recording medium 5. The changeover controller SC hasintensity-receiving-antenna number information N1 andvideo-receiving-antenna number information N2 to make changeoverinstruction of the changeover switches SW based on the numberinformation and to instruct the processing timing of the sample holdcircuit 15, the A/D converter 16 and the selection controller C1. Apower supply unit 17 performs power supply to each unit described above,and is realized by a battery, for example.

The changeover switch SW of the external device 2 b selectively changesover any one of the receiving antennas A1 to An based on a changeoverinstruction from the changeover controller SC, and outputs a radiosignal from the changed receiving antenna A1 to An to the receivingcircuit 11. As described above, the receiving circuit 11 amplifies theradio signal and outputs a demodulated video signal S1 to the signalprocessing circuit 12, and outputs a received intensity signal S2indicating a receiving field intensity of the amplified radio signal tothe sample hold circuit 15. Video data processed by the signalprocessing circuit 12 is stored in the storage unit 13 by the controllerC and displayed by the display unit 14 for output. A signal subjected tosample hold by the sample hold circuit 15 is converted into a digitalsignal by the A/D converter 16 to be fetched by the controller C, andthe selection controller C1 of the controller C selects a receivingantenna having the largest receiving field intensity from among thereceiving field intensities received in an intensity receiving period ina synchronization period described later as a receiving antenna for avideo signal period and outputs it as a signal S4 which assumes areceiving antenna number for receiving in the intensity receiving periodas the intensity-receiving-antenna number information N1 and a receivingantenna number for the video signal period as thevideo-receiving-antenna number information N2 to the changeovercontroller SC. The changeover controller SC holds theintensity-receiving-antenna number information N1 and thevideo-receiving-antenna number information N2 instructed by theselection controller C1, and outputs a signal S5 which instructs thechangeover switch SW to select and connect the receiving antenna A1 toAn corresponding to the intensity-receiving-antenna number informationN1 during the intensity receiving period and instructs the changeoverswitch SW to select and connect the receiving antenna A1 to Ancorresponding to the video-receiving-antenna number information N2during the video receiving period, and outputs a signal S3 a whichinstructs a sample hold timing by the sample hold circuit 15, a signalS3 b which instructs an A/D converting timing by the A/D converter 16,and a signal S3 c which instructs a selection control timing by theselection controller C1.

Detailed structures of the sample hold circuit 15 and the changeoverswitch SW will be described with reference to FIG. 3 and FIG. 4. In FIG.3, the sample hold circuit 15 has a pulse generator 15 a for generatinga sample hold pulse, an intensity receiving sample hold circuit 15 b forsample-holding a receiving field intensity of the intensity receivingperiod, and a video receiving sample hold circuit 15 c forsample-holding a receiving field intensity of the video receivingperiod.

The pulse generator 15 a generates a pulse SH_KYODO and a pulse SH_EIZOwhich indicates a timing and a period of the sample hold by theintensity receiving sample hold circuit 15 b based on the signal S3 ainput from the changeover controller SC. The pulse SH_KYODO and thepulse SH_EIZO are output to the switch SW1 of the intensity receivingsample hold circuit 15 b and the switch SW2 of the video receivingsample hold circuit 15 c, respectively.

The intensity receiving sample hold circuit 15 b buffers the receivedintensity signal S2 input from the receiving circuit 11 by an amplifierAmp1. On the other hand, the switch SW1 enters the ON state during aperiod indicated from the timing indicated by the pulse SH_KYODO,charges are accumulated in a capacitor C1 to enter the OFF state so thatthe accumulated charges are buffered by an amplifier Amp2, andconsequently the signal buffered by the amplifier Amp1 is output as asignal KYODO_LVL indicating the receiving field intensity of theintensity receiving period to the A/D converter 16.

On the other hand, the video receiving sample hold circuit 15 c is inputwith the signal buffered by the amplifier Amp1 from the intensityreceiving sample hold circuit 15 b. The switch SW2 enters the ON stateduring a period indicated from a timing indicated by the pulse SH_EIZO,charges are accumulated in a capacitor C2 to enter the OFF state so thatthe accumulated charges are buffered by an amplifier Amp3, andconsequently the signal buffered by the amplifier Amp1 is output as asignal EIZO_LVL indicating the receiving field intensity of the videosignal period to the A/D converter 16.

A detailed structure of the changeover switch SW will now be described.In FIG. 4, the changeover switch SW has a decoder D1 for decoding a3-bit signal S5 input from the changeover controller SC into an 8-bitsignal S51, a switch SW11 connected to the receiving antennas A1 to A4for selecting any one of them, a switch SW 12 connected to the receivingantennas A5 to A8 for selecting any one of them, a switch SW13 connectedto the switches SW11 and SW 12 for selecting and outputting any one ofsignals Sa and Sb output from the switches SW11 and SW12, respectively,and an inverting circuit I1 for securing exclusive logic of the switchSW13 based on the highest bit input into the decoder.

The signal S5 is input into the decoder D1 as a 3-bit signal forselecting any one of the eight receiving antennas A1 to A8. This 3-bitsignal S5 is a signal ANT_SELECT[0], signal ANT_SELECT[1] and signalANT_SELECT[2], and the signal indicating the highest bit is the signalANT_SELECT[2]. The decoder D1 decodes the 3-bit signal S5 into the 8-bitsignal S51, outputs a lower 4-bit signal S51 a to the switch SW11 forswitching the smaller-numbered receiving antennas A1 to A4, and outputsa higher 4-bit signal S51 b to the switch SW12 for switching thelarger-numbered receiving antennas A5 to A8. The switches SW11 and SW12select any one of the receiving antennas A1 to A8 according to thesignals S51 a and S51 b, respectively. The switch SW13 selects any oneof the signals Sa and Sb output from the switches SW11 and SW12 based onthe highest bit signal ANT_SELECT[2]. When the switch 11 selects any oneof the receiving antennas A1 to A4, the switch SW12 has not selected anyone of the receiving antennas A5 to A8, but has input an invertingsignal of the highest bit signal ANT_SELECT[2] by the inverting circuitI1 and performed exclusive logic in order to increase selectionaccuracy. A signal of the receiving antenna A1 to A8 finally selected bythe switch SW13 is output to the receiving circuit 11. Here, thereceiving antennas A1 to An has been described as the receiving antennasA1 to A8. The antenna number of each receiving antenna A1 to A8 isidentification information unique to each receiving antennas and thenumbers “1” to “8” are assumed as “0” to “7” for the sake of informationprocessing.

The intensity receiving period and video receiving period describedabove with reference to FIG. 5 and FIG. 6, that is, a frame structure ofa radio signal will be described, and an outline of a processing ofselecting and changing over the receiving antennas A1 to An will bedescribed. A radio signal transmitted from the capsule endoscope 3 istransmitted in unit of frame, and this frame is constituted of theintensity receiving period and the video signal period as shown in FIG.5. The intensity receiving period is a period corresponding to apreamble signal period for receiving adjustment. Further, the videosignal period can contain a control signal necessary for receiving avideo signal in addition to the video signal itself.

Each frame may be transmitted as shown in FIG. 6 and a no-signal statemay be between frames, or each frame may be continuously transmitted. Aframe cycle TT for frame transmission is short in an imaging area ofinterest or in an area where the capsule endoscope 3 fast moves inconsideration of effective utilization of the battery of the capsuleendoscope 3, and the length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 6, when the n-th frame (n) and the (n+1)-th frame (n+1)are sequentially transmitted, other receiving antenna (intensityreceiving antenna) different from the receiving antenna (video receivingantenna) for receiving in the video signal period of the same frame (n)is changed over in a period ta corresponding to the intensity receivingperiod of the frame (n), and the video receiving antenna is changed overin a period tb including the video receiving period and a period to thestart of the intensity receiving period of the next frame (n+1).Similarly, in a period ta′ corresponding to the intensity receivingperiod of the frame (n+1), the intensity receiving antenna is changedover in the video signal period of the same frame (n+1) and the videoreceiving antenna is changed over in a period tb′ including the videoreceiving period and a period to the start of the intensity receivingperiod of the next frame (n+2).

At timing t1 in the intensity receiving period of the frame (n), anintensity detection processing is performed by the sample hold circuit15 and the A/D converter 16 and a result thereof is output to theselection controller C1. Similarly, at timing t2 in the video signalperiod of the frame (n), the intensity detection processing is performedby the sample hold circuit 15 and the A/D converter 16 and a resultthereof is output to the selection controller C1. Therefore, a marginperiod to the antenna changeover processing of the next frame (n+1) is achangeover margin time T from timing t2 to the start of the intensityreceiving period of the next frame (n+1). Thus, the timing t2 is set atan earlier point in the video signal period so that the changeovermargin time T can be made long. Due to the long changeover margin timeT, the sample hold circuit 15, the A/D converter 16, the selectionchangeover controller C1, the changeover controller SC and thechangeover switch SW do not require high speed performance and can berealized using a simple circuit apparatus. The receiving field intensityof the receiving antenna for receiving the video signal is received andmeasured in the video signal period and does not require to be measuredin the intensity receiving period so that the antenna does not requireto be changed over at high speed. Further, this results in a changeovermargin because the receiving field intensity of the self-video signaldoes not require to be measured when the receiving field intensities ofa plurality of receiving antennas are measured in the intensityreceiving period.

An antenna changeover processing procedure will be described withreference to a flowchart shown in FIG. 7. The antenna changeoverprocessing is performed by the selection controller C1 and thechangeover controller SC. In FIG. 7, the selection controller C1 firstsets, as initial setting, the video-receiving-antenna number informationas the video receiving antenna number to be No. 1 and theintensity-receiving-antenna number information as the intensityreceiving antenna number to be No. 2, and registers the same in thevideo-receiving-antenna number information N2 and theintensity-receiving-antenna number information N1 in the changeovercontroller SC (step S101). Here, No. 1 to No. n of thevideo-receiving-antenna number information and theintensity-receiving-antenna number information are the numberscorresponding to the receiving antennas A1 to An, respectively.

Thereafter, the changeover controller SC determines whether theintensity receiving period has started (step S102). If the intensityreceiving period has started (step S102, YES), the changeover controllerSC outputs an instruction of changing to the receiving antennacorresponding to the intensity-receiving-antenna number informationregistered in the intensity-receiving-antenna number information N1 tothe changeover switch SW (step S103), and the changeover switch SWchanges to the instructed receiving antenna. Thereafter, the changeovercontroller SC causes the sample hold circuit 15 and the A/D converter 16to perform a processing of detecting the receiving field intensity ofthe intensity receiving antenna at timing t1 (step S104), and instructsthe changeover switch SW to change to the receiving antenna registeredin the video-receiving-antenna number information N2 at the start of thevideo receiving period (step S105) so that the changeover switch SWchanges to the instructed receiving antenna. The changeover time in stepS105 may not be at the start of the video signal period, or may bewithin the intensity receiving period if it is at the end of the fieldintensity measurement processing for the intensity receiving antenna.

Thereafter, the changeover controller SC determines whether the videosignal period has started (step S106). The video signal period used heremay be assumed as a period in which the video signal is transmitted ifthe control signal or the like is included in the video signal period.Thereafter, if the video signal period has started (Step S106, YES), thesample hold circuit 15 and the A/D converter 16 are caused to performthe processing of detecting the receiving field intensity of theintensity receiving antenna at timing t2 (step S107).

Thereafter, the selection controller C1 determines whether the receivingfield intensity of the video receiving antenna received in the videosignal period (video receiving antenna intensity) is smaller than thereceiving field intensity of the intensity receiving antenna received inthe intensity receiving period (intensity receiving antenna intensity)(step S108). If the video receiving antenna intensity is smaller thanthe intensity receiving antenna intensity (step S108, YES), thevideo-receiving-antenna number information is registered in theintensity-receiving-antenna number information N1 as theintensity-receiving-antenna number information (step S109), and theprocessing proceeds to step S110. On the other hand, if the videoreceiving antenna intensity is not smaller than the intensity receivingantenna intensity (step S108, NO), that is, when the video receivingantenna intensity exceeds the intensity receiving antenna intensity, thevalue of the intensity-receiving-antenna number information N1 isincremented as it is (step S110).

Thereafter, it is determined whether the value of theintensity-receiving-antenna number information coincides with the valueof the video-receiving-antenna number information (step S111), if itcoincides therewith (step S111, YES), the processing proceeds to stepS110 to increment the value of the intensity-receiving-antenna numberinformation, and if it does not coincides therewith (step S111, NO), itis further determined whether the intensity-receiving-antenna numberinformation is No. n (step S112). If the intensity-receiving-antennanumber information is not No. n (step S112, NO), the processing proceedsto step S102 to repeat the above processing, and if theintensity-receiving-antenna number information is No. n (step S112,YES), it is further determined whether the video-receiving-antennanumber information is No. 1 (step S113). If the video-receiving-antennanumber information is not No. 1 (step S113, NO), theintensity-receiving-antenna number information is set and registered tobe No. 1 (step S114), and if the video-receiving-antenna numberinformation is No. 1 (step S113, YES), the intensity-receiving-antennanumber information is set and registered to be No. 2 (step S115), andthen the processing proceeds to step S102 to repeat the aboveprocessing.

Since the first embodiment is constituted to measure the receiving fieldintensity of the video signal in the video signal period, tosequentially change to the receiving antenna other than the receivingantenna for receiving the video signal in the intensity receiving periodto measure the receiving field intensity, and to change the receivingantenna changed in the intensity receiving period to the receivingantenna for the video receiving period when the receiving fieldintensity measured in the intensity receiving period exceeds thereceiving field intensity measured in the video receiving period, theintensity receiving period can be reduced, a margin can be allowed inthe time to change over the receiving antenna in the intensity receivingperiod, the intensity detection timing is made earlier in the videoreceiving period so that a time margin can be allowed in the antennachangeover setting between frames, and consequently high speedperformance is not required for the structure on the receiving fieldintensity measurement, thereby achieving the simple structure.

A second embodiment according to the present invention will now bedescribed. The second embodiment is constituted so that a peak holdcircuit 18 is further provided between the receiving circuit 11 and thesample hold circuit 15 according to the first embodiment.

FIG. 8 is a block diagram showing a structure of a receiving apparatusaccording to the second embodiment of the present invention. As shown inFIG. 8, the receiving apparatus is provided with the peak hold circuit18 and holds a peak value of the received intensity signal S2 outputfrom the receiving circuit 11.

Thus, as shown in FIG. 9, the changeover controller SC outputs a signalSr to the peak hold circuit 18 at the start of the intensity receivingperiod and resets it at timing tr1. Thereafter, the changeovercontroller SC acquires a peak value held by the peak hold circuit 18 atdetection timing t3 of the sample hold circuit 15, and again resets thepeak hold circuit 18 at timing tr2 at the start of the video signalperiod. The sample hold circuit 15 acquires the peak value held by thepeak hold circuit 18 at timing t4 after timing tr2. In other words, thesample hold circuit 15 can sample the peak value between timing tr1 andtiming t3 and can sample the peak value between timing tr2 and timingtr4, thereby performing the receiving field intensity measurement withhigher accuracy.

A third embodiment according to the present invention will now bedescribed. The third embodiment is constituted so that the receivingfield intensity measurement for all the receiving antennas is performedin the intensity receiving period to select a receiving antenna havingthe largest receiving field intensity as the video receiving antenna.FIG. 10 is a block diagram showing a structure of a receiving apparatusaccording to the third embodiment of the present invention. As shown inFIG. 10, the receiving apparatus is provided with a selection controllerC3 instead of the selection controller C1. Other configurations areidentical to those in the first embodiment and like numerals are denotedto like configurations.

The intensity receiving period and video receiving period describedabove with reference to FIG. 11, that is, the frame structure of a radiosignal will be described, and an outline of a processing of selectingand changing over the receiving antennas A1 to An will be described. Aradio signal transmitted from the capsule endoscope 3 is transmitted inunit of frame and is constituted of the synchronization period and thevideo signal period as shown in FIG. 11. The synchronization period is aperiod corresponding to the preamble signal period for receivingadjustment. Further, the video signal period can contain a controlsignal necessary for receiving the video signal in addition to the videosignal itself.

Each frame is transmitted as shown in FIG. 11 and a no-signal state maybe between frames or each frame may be continuously transmitted. A framecycle TT for frame transmission is short in an imaging area of interestor in an area where the capsule endoscope 3 fast moves in considerationof effective utilization of the battery of the capsule endoscope 3, andthe length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 11, the synchronization period TS in the n-th frame (n)has an intensity receiving period TS1 for selecting a receiving antennahaving the largest receiving field intensity and a synchronizationperiod TS2 for the video signal, and antenna changeover is performedbetween the intensity receiving period TS1 and the synchronizationperiod TS2. Here, when the receiving antennas A1 to An are eightreceiving antennas, the antenna changeover of all the receiving antennasA1 to A8 is performed in the intensity receiving period TS1 and thereceiving field intensity measurement is performed at timings t1 to t8within the period of each changed state. Peak hold pulses at timings t1to t8 are generated by the pulse generator 15 a.

When the receiving field intensity measurement for all the receivingantennas A1 to A8 is terminated, the selection controller C3 selects areceiving antenna having the largest receiving field intensity at thepoint and selects the receiving antenna as the video receiving antennain the synchronization period TS2 and video signal period TM. Thereceiving field intensity measurement by the video receiving antenna isperformed in the video signal period TM or synchronization period TS2 attiming tt1 or timing tta. The receiving field intensity measurement bythe video receiving antenna may not be performed if not needed. It isperformed for receiving state confirmation in the third embodiment.

Since the third embodiment is constituted so that the receiving fieldintensity measurement for all the receiving antennas is performed in theintensity receiving period TS1 to select a receiving antenna having thelargest receiving field intensity as the video receiving antenna, lessvideo signals are transmitted in vain and a small number of videosignals can be securely received. Consequently, power saving of thecapsule endoscope 3 can be promoted.

A fourth embodiment according to the present invention will now bedescribed. The forth embodiment is constituted so that the result of thereceiving field intensity measurement by the video receiving antenna iseffectively utilized to select and process the video receiving antenna.

FIG. 12 is a block diagram showing a structure of a receiving apparatusaccording to the fourth embodiment of the present invention. As shown inFIG. 12, the receiving apparatus is provided with a selection controllerC4 instead of the selection controller C1. Other configurations areidentical to those in the first embodiment and like numerals are denotedto like configurations.

The selection controller C4, as shown in FIG. 13, excludes the receivingantenna selected as the video signal antenna in the frame (n−1) from theintensity receiving antennas, and assumes the remaining seven receivingantennas as the intensity receiving antennas to cause them to performthe receiving field intensity measurement for each receiving antenna inthe intensity receiving period TS1. The selection controller C4determines the receiving antenna having the largest receiving fieldintensity in the intensity receiving period TS1, and compares thereceiving field intensity of the determined receiving antenna with thereceiving field intensity of the video receiving antenna in the frame(n−1) to select the receiving antenna having the higher receiving fieldintensity as the video receiving antenna for the frame (n). The selectedvideo receiving antenna measures the receiving field intensity in thesynchronization period TS2 or video signal period TM and a resultthereof is used to determine the video receiving antenna for the frame(n+1).

Since the fourth embodiment is constituted so that the receiving fieldintensity of the video receiving antenna is measured in the previousvideo signal period TM having a time margin and only the receivingantenna is excluded from the intensity receiving antennas in theintensity receiving period TS1 to select a receiving antenna having thelargest receiving field intensity from among the receiving fieldintensities as the video receiving antenna, secure video signals can bereceived in a short time.

Although all the receiving antennas are basically assumed as theintensity receiving antennas in the aforementioned third and fourthembodiments, if all the receiving antennas are previously grouped, forexample, only the grouped antennas are basically subjected to theintensity receiving antennas. Further, not all the receiving antennasbut near receiving antennas predetermined for the video receivingantenna may be targeted. For example, when all the receiving antennasare denoted with serial numbers corresponding to the moving path of thecapsule endoscope 3, the receiving antennas near the video receivingantenna, for example, having the previous and next two serial numbersmay be targeted. When the receiving antennas are denoted with serialnumbers, all the receiving antennas having larger numbers than that ofthe current video receiving antenna are subjected to the intensityreceiving antennas.

A fifth embodiment according to the present invention will now bedescribed. The fifth embodiment is constituted so that the intensityreceiving period is provided within the synchronization period and thesynchronization signal is used to perform the receiving field intensitymeasurement during the intensity receiving period. FIG. 14 is a blockdiagram showing a structure of a receiving apparatus according to thefifth embodiment of the present invention. As shown in FIG. 14, thisreceiving apparatus is provided with a selection controller C5 insteadof the selection controller C1. Other configurations are identical tothose in the first embodiment and like numerals are denoted to likeconfigurations.

Here, the intensity receiving period and video receiving perioddescribed above with reference to FIG. 15 and FIG. 16, that is, theframe structure of a radio signal will be described and an outline of aprocessing of selecting and changing over the receiving antennas A1 toAn will be described. A radio signal transmitted from the capsuleendoscope 3 is transmitted in unit of frame, and in this frame, thevideo signal period is conventionally provided after the intensityreceiving period TS1, the synchronization period TS is provided at thehead of the video signal period, and the video period TM made of m linesis provided subsequent to the synchronization period TS. In the fifthembodiment, the intensity receiving period TS1 is shifted to thesynchronization period TS side and the synchronization signal is used asa signal for the receiving field intensity measurement. Thesynchronization signal is a pulse signal having a duty ratio of 50%, forexample. When the receiving circuit 11 is constituted to be separatedinto an RF module for performing RF signal processing and a demodulatingcircuit for performing baseband demodulation, the synchronizationprocessing for the RF module is performed in the first half of thesynchronization period TS, and then the synchronization processing forthe demodulating circuit is performed in the second half of thesynchronization period TS.

Each frame is transmitted as shown in FIG. 15 and a no-signal state maybe between frames or each frame may be continuously transmitted. A framecycle TT for frame transmission is short in an imaging area of interestor in an area where the capsule endoscope 3 fast moves in considerationof effective utilization of the battery of the capsule endoscope 3, andthe length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 16, the synchronization period TS in the n-th frame (n)has the intensity receiving period TS1 for selecting a receiving antennahaving the largest receiving field intensity by using thesynchronization signal and the synchronization period TS2 for the videosignal, and antenna changeover is performed between the intensityreceiving period TS1 and the synchronization period TS2. In FIG. 16, thesynchronization signal is used in the intensity receiving period TS1 tochange over two receiving antennas, and the receiving field intensity ofeach receiving antenna is sample-held and received at timings t1, t2corresponding to the changed state, respectively. Thereafter, thereceiving antenna for receiving the video signal is changed at timing tcwithin the synchronization period TS. The receiving circuit 11 performsthe synchronization processing subsequent to the synchronization periodcorresponding to the intensity receiving period TS1 in the changedsynchronization period TS2. Thereafter, the video signal made of m linesis received in the video period TM. The receiving field intensity of thevideo receiving antenna is measured at, for example, timing tt1 in thesynchronization period TS2 and video period TM. The sample hold pulsesat timings t1, t2, tt1 and tta are generated by the pulse generator 15a.

The selection controller C5 is constituted to select a receiving antennahaving the largest receiving field intensity from among the receivingfield intensities received in the intensity receiving period TS1 as thereceiving antenna for the video signal period, but is not limitedthereto and may be constituted to select a receiving antenna having thelargest receiving field intensity, including the receiving fieldintensity of the video receiving antenna in addition to the receivingfield intensities of the receiving antennas received in thesynchronization period TS1, as the video receiving antenna.

The fifth embodiment is constituted so that the intensity receivingperiod TS1 is contained in the synchronization period TS, but is notlimited thereto and may be constituted so that part of the intensityreceiving period TS1 is overlapped on the synchronization period TS.

Since the fifth embodiment is constituted so that the intensityreceiving period TS1 is provided in the synchronization period TS andthe synchronization signal is used to perform the receiving fieldintensity measurement in the intensity receiving period TS1, theintensity receiving period does not require to be newly provided,thereby reducing the transmission power of the capsule endoscope 3 to beconsumed per frame.

A sixth embodiment according to the present invention will now bedescribed. A wireless in-subject information acquiring system shown inthe sixth embodiment corresponds to the transmitting/receiving systemand uses a capsule endoscope as one example of the transmittingapparatus (in-subject introducing apparatus).

FIG. 17 is a block diagram schematically showing a structure of thecapsule endoscope 3 according to the sixth embodiment of the presentinvention. As shown in FIG. 17, the capsule endoscope 3 comprises a LED19 for radiating an imaging area when imaging the inside of the subject1, a LED drive circuit 20 for controlling a drive state of the LED 19, aCCD 21 as imaging means for imaging an area radiated by the LED 19, anda signal processing circuit 22 for processing an image signal outputfrom the CCD 21 into imaging information in a desired form. The capsuleendoscope 3 further comprises a CCD drive circuit 25 for controlling adrive state of the CCD 21, an RF transmitting unit 23 for modulatingimage data imaged by the CCD 21 and processed by the signal processingcircuit 22 to generate an RF signal, a transmitting antenna unit 24 fortransmitting an RF signal output from the RF transmitting unit 23, and asystem control circuit 26 for controlling operations of the LED drivecircuit 20, the CCD drive circuit 25 and the RF transmitting unit 23.The CCD 21, the signal processing circuit 22 and the CCD drive circuit25 are collectively called an imaging circuit 27.

The capsule endoscope 3 comprises the above mechanism to acquire imageinformation of an inspected site radiated by the LED 19 through the CCD21 while it is being introduced into the subject 1. The acquired imageinformation is signal-processed into a video signal by the signalprocessing circuit 22 and converted into an RF signal in the RFtransmitting unit 23, and then is transmitted to the outside via thetransmitting antenna unit 24.

The signal processing circuit 22 comprises a dummy signal adder 22 a,and the dummy signal adder 22 a adds a dummy pulse for receivingintensity measurement used when synchronizing with the horizontalsynchronization signal and the vertical synchronization signal of thevideo signal and detecting the receiving field intensity of eachreceiving antenna from a radio signal received by each receiving antennadescribed later within the vertical blanking period. For example, acounter is provided which is synchronized with the horizontalsynchronization signal and the vertical synchronization signal, and adummy pulse is generated by using a count value of the counter as areference to be embedded in the vertical blanking period. The positionor frequency of the dummy pulse is arbitrary if it is in the verticalblanking period.

The capsule endoscope 3 comprises a sensor unit 35 for detecting asignal of predetermined magnetism, light, radio wave or the like, and adrive control unit 34 for controlling the drive of the system controlcircuit 26 for entirely controlling the processings of the LED drivecircuit, the CCD drive circuit 25, the RF transmitting unit 23 and therespective units. The sensor unit 35 is realized by, for example, a pHsensor, and detects whether the capsule endoscope 3 has reached apredetermined position in the subject so that the drive control unit 34controls the driving of each unit based on the result. Thus, the powerconsumption can be restricted.

The drive control unit 34 is supplied with power for a battery 40 as anenergy supply source via a power supply switch 33 in a power supplyswitch circuit 30. The battery 40 is realized by a button battery madeof silver oxide, for example. The power supply switch 33 is a so-calledmain power supply switch of the capsule endoscope 3. The power supplyswitch circuit 30 further has a signal detecting circuit 31 and a switchcontrol circuit 32. The signal detecting circuit 31 as external signaldetecting means for detecting a signal from the outside of the capsuleendoscope 3 is realized by a reed switch and is turned ON/OFF throughproximity/separation of a magnet 50 with respect to the reed switch. Inother words, the switch control circuit 32 which ON/OFF operatesdepending on whether a magnetic force acts on the reed switch controlsto cause ON/OFF of the power supply switch 33 to perform toggleoperation based on a control signal, that is, an ON/OFF signal from thesignal detecting circuit 31. The ON/OFF of the power supply switch 33 bythe magnet 50 is performed before being introduced into the subject toperform operation check of the capsule endoscope 3.

FIG. 18 is a block diagram showing a structure of a receiving apparatusaccording to the sixth embodiment of the present invention. As shown inFIG. 18, the receiving apparatus is provided with a selection controllerC6 instead of the selection controller C1. Other configurations areidentical to those in the first embodiment and like numerals are denotedto like configurations.

Here, the synchronization period and video receiving period describedabove with reference to FIG. 19 and FIG. 20, that is, the framestructure of a radio signal will be described, and a processing ofselecting and changing over the receiving antennas A1 to An will bedescribed. A radio signal transmitted from the capsule endoscope 3 istransmitted in unit of frame, and the frame is constituted, as shown inFIG. 19, of the synchronization period TS as the additional partincluding information for synchronization and the video signal period TMas the information body part including information body. Thesynchronization period TS is a period corresponding to the preamblesignal period for receiving adjustment. Further, the video signal periodTM is a period for receiving a video signal, and the video signal has afield period TF1 in which odd-numbered field signals are transmitted, avertical blanking period TV and a field TF2 in which even-numbered fieldsignals are transmitted. A dummy pulse P added by the dummy signal adder22 a is inserted into the vertical blanking period TV as describedabove. A control signal necessary for receiving the video signal may beincluded in the video signal period TM in addition to the horizontalvideo signal itself. The synchronization period and the video receivingperiod may be provided as independent periods or may be provided asoverlapped periods.

Each frame is transmitted as shown in FIG. 20 and a no-signal state maybe between frames or each frame may be continuously transmitted. A framecycle TT for frame transmission is short in an imaging area of interestor in an area where the capsule endoscope 3 fast moves in considerationof effective utilization of the battery of the capsule endoscope 3, andthe length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 20, the receiving antenna is changed over between thefield periods TF1, TF2 and the vertical blanking period TV in the n-thframe (n). The video receiving antenna stands for a receiving antennafor receiving in the synchronization period TS and each field periodTF1, TF2. The intensity receiving antenna stands for a receiving antennafor receiving in the vertical blanking period TV. The selectioncontroller C1 measures the receiving field intensity in the period forchanging to the intensity receiving antenna, selects and changes areceiving antenna having the largest receiving field intensity includingthe receiving field intensity of the current video receiving antenna asthe receiving antenna in the period for changing to the next videoreceiving antenna, and selects the intensity receiving antenna exceptfor at least the immediately previous video receiving antenna in theperiod for changing to the next intensity receiving antenna. A receivingantenna having the largest receiving field intensity at the point isselected as the video receiving antenna through the above repetition.

A timing at which the receiving antenna having the largest receivingfield intensity is selected may be selected after a predetermined numberof times of the receiving field intensity measurement, and the videoreceiving antenna selected at the previous time may be selected duringthe measurement. Since the moving path of the capsule endoscope 3 ispreviously known, the odd-numbered field in the frame to be firsttransmitted previously selects the video receiving antenna and the videoreceiving antenna of the odd-numbered field in the second and subsequentframes may set the receiving antenna selected in the vertical blankingperiod TV in the first frame.

In FIG. 20, the receiving field intensity measurement is performed twiceat timings t1 and t2 in the vertical blanking period TV, but is notlimited thereto and may be performed only one time or more than threetimes. When performing the receiving field intensity measurement severaltimes, it is preferable to perform the receiving field intensitymeasurement for different receiving antennas. The field intensity of thevideo receiving antenna is measured at timing tt1 in the field periodTF1, but the receiving field intensity may be measured at timing tta inthe synchronization period TS. The timings t1, t2, tt1 and tt2 arepulses generated by the pulse generator 15 a. Here, the receiving fieldintensity measurement is performed in the horizontal blanking period TVadded with a dummy pulse P, but even when the dummy pulse is added tothe entire vertical blanking period TV, the receiving field intensitymeasurement may not be performed for the entire horizontal blankingperiod TV.

The antenna changeover between the field period TF1, TF2 and thevertical blanking period TV is possible with high accuracy because itcan use the synchronization of the vertical blanking period.

The synchronization period TS is about 3 ms, and a period as long as thesynchronization period TS may be added before the synchronization periodas a period for the receiving field measurement to measure the receivingfield intensity. But, since the vertical blanking period TV is a periodof 100 ms or more, the receiving field intensity for many receivingantennas can be measured in the period. Naturally, the synchronizationperiod for the receiving field measurement may be a format to be addedbefore the synchronization period TS.

Since the sixth embodiment is constituted so that the dummy pulse P forthe receiving field intensity measurement is added to the verticalblanking period TV to perform the receiving field intensity measurementfor selecting the video receiving antenna in the long vertical blankingperiod TV, the optimum video receiving antenna having the largestreceiving field intensity can be selected with high accuracy. Further,the synchronization period can be reduced and consequently thetransmission time in the frame is reduced, thereby achieving powersaving of the capsule endoscope 3.

In the sixth embodiment, description is made as each frame beingtransmitted without synchronization between frames, but in the case of2-frame transmission, it is preferable that the vertical blanking periodis provided between frames and the receiving field intensity measurementfor selecting the optimum video receiving antenna is performed even inthe vertical blanking period similarly as in the vertical blankingperiod between the fields TF1 and TF2 (refer to FIG. 21). Further,although the imaging in an interlace manner has been described in theaforementioned sixth embodiment, in the case of the interlace manner, ifthe frames are continuously transmitted, the vertical blanking period TVoccurs, thereby applying the present embodiment.

A seventh embodiment according to the present invention will now bedescribed. The seventh embodiment is constituted so that a dummy pulsefor the receiving field intensity measurement is added in the horizontalblanking period in the video signal period to perform the receivingfield intensity measurement for selecting the video receiving antenna inthe long horizontal blanking period.

FIG. 22 is a block diagram schematically showing a structure of acapsule endoscope according to the seventh embodiment of the presentinvention. As shown in FIG. 22, the capsule endoscope 3 is provided witha dummy signal adder 22 b instead of the dummy signal adder 22 a shownin FIG. 17 a. Further, FIG. 23 is a block diagram showing a structure ofa receiving apparatus according to the seventh embodiment of the presentinvention. As shown in FIG. 23, the receiving apparatus is provided witha selection controller C7 instead of the selection controller C1. Otherconfigurations are identical to those in the sixth embodiment and likenumerals are denoted to like configurations.

As shown in FIG. 22, the signal processing circuit 22 comprises thedummy signal adder 22 b, and the dummy signal adder 22 b adds a dummypulse for the receiving intensity measurement used when synchronizingwith the horizontal synchronization signal and vertical synchronizationsignal of the video signal and detecting the receiving field intensityof each antenna from the radio signal received by each receiving antennadescribed later during the horizontal blanking period. For example, acounter is provided which synchronizes with the horizontalsynchronization signal and the vertical synchronization signal, and adummy pulse is generated by using a count value of the counter as areference to be embedded in the horizontal blanking period. The positionor frequency of the dummy pulse is arbitrary if it is in the horizontalblanking period. It is not necessary to add the dummy pulse to all thehorizontal blanking periods, and the dummy pulse may be added to onlythe required horizontal blanking periods.

The synchronization period and video receiving period described abovewith reference to FIG. 24 and FIG. 25, that is, the frame structure of aradio signal will be described and a processing of selecting andchanging over the receiving antennas A1 to An will be described. A radiosignal transmitted from the capsule endoscope 3 is transmitted in unitof frame, and, as shown in FIG. 24, the frame is constituted of thesynchronization period TS as the additional part including informationfor synchronization and the video signal period TM as the informationbody part including information body. The synchronization period TS is aperiod corresponding to the preamble signal period for receivingadjustment. The video signal period TM is a period for receiving a videosignal, and the video signal has a video line period TH in which a videoline signal for each line is transmitted and a horizontal blankingperiod Th inserted between the video line periods TH. A dummy pulse Padded by the dummy signal adder 22 a is inserted into the horizontalblanking period Th as described above. The video signal period TM cancontain a control signal necessary for receiving the video signal inaddition to the horizontal video signal itself. The synchronizationperiod and the video receiving period may be provided as independentperiods or may be provided as overlapped periods.

Each frame is transmitted as shown in FIG. 25 and a no-signal state maybe between frames or each frame may be continuously transmitted. A framecycle TT for frame transmission is short in an imaging area of interestor in an area where the capsule endoscope 3 fast moves in considerationof effective utilization of the battery of the capsule endoscope 3, andthe length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 25, the receiving antenna is changed over at timing tcin the synchronization period TS in the n-th frame (n) and the receivingantenna is changed over between the video line period TH and thehorizontal blanking period Th. The video receiving antenna stands for areceiving antenna for receiving in a period TSH after timing tc in thesynchronization period TS and the video line period TH at the first lineas well as each video line period TH after the second line. Theintensity receiving antenna stands for a receiving antenna for receivingin a period TSS before timing tc in the synchronization period TS andeach horizontal blanking period Th. The selection controller C1 measuresthe receiving field intensity in a period for changing to the intensityreceiving antenna, selects and changes a receiving antenna having thelargest receiving field intensity including the receiving fieldintensity of the current video receiving antenna as the receivingantenna in a period for changing to the next video receiving antenna,and selects the intensity receiving antenna except for at least theimmediately previous video receiving antenna in a period for changing tothe next intensity receiving antenna. A receiving antenna having thelargest receiving field intensity at the point is selected as the videoreceiving antenna through the above repetition.

The timing at which the receiving antenna having the largest receivingfield intensity is selected may be selected after a predetermined numberof times of the receiving field intensity measurement, and the videoreceiving antenna selected at the previous time may be selected. Forexample, the video receiving antenna may be selected and determined inunit of frame. In this case, the video receiving antenna selected anddetermined in the frame (n) is used as the video receiving antenna inthe next frame (n+1).

In FIG. 25, the receiving field intensity measurement is performed oncein the period TSS before timing tc in the synchronization period TS andeach horizontal blanking period Th, respectively, but is not limitedthereto and the receiving field intensity measurement may be performedseveral times, and in this case, the receiving field intensitymeasurement for a plurality of different receiving antennas may beperformed. The timings t0 to t2 and tt1 to tt3 are pulses generated bythe pulse generator 15 a. Here, although the receiving field intensitymeasurement is performed in the horizontal blanking period Th added withthe dummy pulses P, even when the dummy pulses are added to all thehorizontal blanking periods Th, the receiving field intensitymeasurement may not be performed for all the horizontal blanking periodsTh.

The antenna changeover between the video line period TH and thehorizontal blanking period Th is possible with high accuracy because itcan use the synchronization of the horizontal blanking.

Since the seventh embodiment is constituted so that the dummy pulse Pfor the receiving field intensity measurement is added in the horizontalblanking period Th in the video signal period TM to perform thereceiving field intensity measurement for selecting the video receivingantenna in the long horizontal blanking period Th, the optimum videoreceiving antenna having the largest receiving field intensity can beselected with high accuracy and fineness.

In the aforementioned seventh embodiment, although the antennachangeover is performed at timing tc in the synchronization period TS,since the receiving field intensity measurement sufficient for selectingthe optimum video receiving antenna can be performed only in thehorizontal blanking period Th, it is preferable that the synchronizationperiod TSS is deleted to assume the synchronization period TSH havingonly the period TSH necessary for the synchronization of the videosignal receiving as shown in FIG. 26. In this case, the synchronizationperiod can be reduced and consequently the transmission time in theframe is reduced, thereby achieving the power saving of the capsuleendoscope 3.

An eighth embodiment according to the present invention will now bedescribed. The eighth embodiment is constituted so that only thereceiving antennas A1 to An connected to the changeover switches are setas the intensity receiving antennas.

FIG. 27 is a block diagram showing a structure of a receiving apparatusaccording to the eighth embodiment of the present invention. As shown inFIG. 27, the receiving apparatus is provided with a changeover switchSW2 having a connecting unit COM with connectors CON1 to CONn instead ofthe changeover switch SW and a selection controller C8 instead of theselection controller C1. Other configurations are identical to those inthe first embodiment and like numerals are denoted to likeconfigurations.

The changeover switch SW2 of the external device 2 b selectively changesany one of the receiving antennas A1 to An based on the changeoverinstruction from the changeover controller SC, and outputs a radiosignal from the changed receiving antenna A1 to An to the receivingcircuit 11. Here, the changeover switch SW2 has the connecting unit CONas antenna changeover means for connecting each receiving antenna A1 toAn in correspondence to the arrangement position of the receivingantenna A1 to An. On the other hand, each receiving antenna A1 to An hasa connector CON1 to CONn connected to the connecting unit CON.

The connecting unit CON has a detecting function of detecting aconnection state of each connector CON1 to CONn. For example, theconnecting unit CON has a detecting circuit as shown in FIG. 28 for theconnector CON1 and has a similar detecting circuit also for otherconnector CON2 to CONn. In FIG. 28, the connector CON1 connects a signalline LS and an earth line LG from the receiving antenna A1 to theconnecting unit CON and branches the earth line LG for output. Theconnecting unit CON outputs the signal line LS to the changeover unitSW1 as it is, which is changed over based on the signal S5 instructingthe changeover and is output to the receiving circuit 11. On the otherhand, one end of the earth line LG is grounded as it is and the otherend of the earth line LG is connected to a constant voltage source VDD.When the connector CON1 is connected to the connecting unit CON, avoltage signal from the constant voltage source VDD flows to one end ofthe earth line LG so that a signal S6 is not output to the selectioncontroller C1 of the external controller C, and when the connector CON1is not connected to the connecting unit CON, the voltage signal from theconstant voltage source VDD is output to the selection controller C1 asthe signal S6 as it is. Therefore, the selection controller C1 detectsthe presence of the signal S6 as the voltage signal to determine whetherthe connector CON1, that is, the receiving antenna A1 is connected. Asimilar detecting circuit is provided in correspondence to eachconnector CON2 to CONn so that the selection controller C1 can sensesthe connection state of each receiving antenna A1 to An.

In FIG. 27, the receiving circuit 11 amplifies a radio signal andoutputs the demodulated video signal S1 to the signal processing circuit12, and outputs the received intensity signal S2 indicating thereceiving field intensity of the amplified radio signal to the samplehold circuit 15. The video data processed by the signal processingcircuit 12 is stored in the storage unit 13 by the controller C, and isdisplayed and output by the display unit 14. The signal subjected tosample-hold by the sample hold circuit 15 is converted into a digitalsignal by the A/D converter 16 to be fetched in the controller C, andthe selection controller C1 of the controller C selects a receivingantenna having the largest receiving field intensity from among thereceiving field intensities received in the intensity receiving perioddescribed later as the receiving antenna for the video signal period,and sequentially selects the receiving antenna other than the selectedreceiving antenna as the receiving antenna for the intensity receivingperiod, and outputs it as the signal S4 which assumes the respectivereceiving antenna numbers as the video-receiving-antenna numberinformation N2 and the intensity-receiving-antenna number information N1to the changeover controller SC. Here, the selection controller C1 setsonly the currently connected receiving antenna A1 to An based on thesignal S6 as the receiving antenna to be changed over. Further, thecontroller C stores the receiving field intensity in the intensityreceiving period and the receiving field intensity in the videoreceiving period in the storage unit 13 together with the video data incorrespondence to the selected receiving antenna. The stored receivingfield intensity of each receiving antenna is information for calculatingthe position of the capsule endoscope 3 in the body when the video datais received.

Here, the intensity receiving period and video receiving perioddescribed above with reference to FIG. 5 and FIG. 29, that is, the framestructure of a radio signal will be described and an outline of aprocessing of selecting and changing over the receiving antenna A1 to Anwill be described. A radio signal transmitted from the capsule endoscope3 is transmitted in unit of frame, and as shown in FIG. 5, the frame isconstituted of the intensity receiving period as the additional partincluding information for the receiving field intensity measurement andthe video signal period as the information body part includinginformation body. The intensity receiving period is a periodcorresponding to the preamble signal period for receiving adjustment.Further, the video signal period can contain a control signal necessaryfor receiving the video signal in addition to the video signal itself.The intensity receiving period and the video receiving period may beprovided as independent periods or may be provided as overlappedperiods.

Each frame is transmitted as shown in FIG. 29 and a no-signal state maybe between frames or each frame may be continuously transmitted. A framecycle TT for frame transmission is short in an imaging area of interestor in an area where the capsule endoscope 3 fast moves in considerationof effective utilization of the battery of the capsule endoscope 3, andthe length of the frame cycle TT is flexibly adjusted.

As shown in FIG. 29, when the n-th frame (n) and the (n+1)-th frame(n+1) are sequentially transmitted, other receiving antenna (intensityreceiving antenna) different from the receiving antenna (video receivingantenna) for receiving in the video signal period of the same frame (n)is changed over in the period ta corresponding to the intensityreceiving period of the frame (n) and the video receiving antenna ischanged over in the period tb including the video receiving period andthe period to the start of the intensity receiving period of the nextframe (n+1). Similarly, the intensity receiving antenna is changed overin the video signal period of the same frame (n+1) in a period ta′corresponding to the intensity receiving period of the frame (n+1), andthe video receiving antenna is changed over in a period tb′ includingthe video receiving period and the period to the start of the intensityreceiving period of the next frame (n+2).

The intensity detection processing is performed by the sample holdcircuit 15 and the A/D converter 16 at timing t1, t1′ during theintensity receiving period of the frame (n) and the frame (n+1), and theresult thereof is output to the selection controller C1. When fastchangeover of the receiving antenna or fast receiving field intensitymeasurement processing is possible, a plurality of intensity receivingantennas may be changed over in the intensity receiving period tomeasure a plurality of receiving field intensities. For example, asshown in FIG. 29, the receiving field intensity may be sequentiallymeasured at timings t2 and t3 after timing t1, and the receiving fieldintensity may be sequentially measured at timings t2′ and t3′ aftertiming t1′.

Here, the antenna changeover processing procedure will be described withreference to a flowchart shown in FIG. 30. In FIG. 30, the selectioncontroller C8 first detects the connection state of the connector CON1to CONn based on the signal S6 (step S201). Thereafter, the receivingantenna A1 to An corresponding to the connected connector CON1 to CONnis set as the intensity receiving antenna (step S202). Thereafter, thereceiving field intensity of each set intensity receiving antenna ismeasured (step S203), and an intensity receiving antenna having thelargest receiving field intensity is set as the video receiving antenna(step S204). Thereafter, the video signal for one frame is received bythe video receiving antenna (step S205).

Thereafter, it is determined whether the connection state of theconnector CON1 to CONn has changed (step S206). If the connections statehas changed (step S206, YES), the processing proceeds to step S202,where the receiving antenna connected after the change is reset as theintensity receiving antenna and the above processing is repeated. On theother hand, if the connection state has not changed (step S206, NO), theprocessing proceeds to step S203, where the above processing is repeatedto perform the changeover processing to the optimum video receivingantenna.

For example, there will be considered a case where as shown in FIG. 31A,there are the receiving antennas A1 to A6 corresponding to sixarrangement positions “1” to “6”, each receiving antenna A1 to A6comprises the connector CON1 to CON6, respectively, the connectors CON1to CON4 are connected to the corresponding connecting portions of theconnecting unit CON, respectively, and the connectors CON5 and CON6 arenot connected thereto. In this case, since it is detected that only thereceiving antennas A1 to A4 are connected, the receiving antennas A1 toA4 are set as the intensity receiving antennas, and the video receivingantenna having the largest receiving field intensity is selected fromamong the receiving antennas A1 to A4.

Thereafter, when the connectors CON1 and CON2 are disconnected and theconnectors CON5 and CON6 are newly connected as shown in FIG. 31B, theselection controller C1 sets only the receiving antennas A3 to A6 as theintensity receiving antennas, and an intensity receiving antenna havingthe largest receiving field intensity is selected as the video receivingantenna from among the intensity receiving antennas.

Since the eighth embodiment is constituted so that only the connectedreceiving antennas A1 to An out of the connector CON1 to CONn are set asthe intensity receiving antennas, the time to measure the receivingfield intensity for all the intensity receiving antennas is reduced,thereby reducing the time for the antenna changeover processing.Particularly, when only the antenna corresponding to the site to beobserved in the body is connected or the number of antennas to be usedin a patient having small stature is reduced, it is possible to securelyacquire necessary receiving images with simple changeover processing.

A ninth embodiment according to the present invention will now bedescribed. Although the aforementioned eighth embodiment is constitutedto comprise all the receiving antennas A1 to An corresponding to thearrangement positions “1” to “6” and to select the intensity receivingantenna based on the presence of the connection with the correspondingconnector CON1 to CONn, the ninth embodiment is constituted so that onlythe receiving antennas necessary for acquiring the antenna receivingfield intensity, on which the image receiving and the positioncalculation of the capsule endoscope 3 are based, are connected toreduce the number of receiving antennas A1 to An so that a reducednumber of receiving antennas are reused to efficiently acquire thereceiving image and the antenna receiving field intensity. For example,there is constituted so that the antenna at the position unnecessary forthe receiving is replaced and reused at a position necessary for thereceiving along with the movement of the capsule endoscope 3 in thebody.

In other words, the structures of the connectors CON1 to CONn of thereceiving antennas A1 to An are made identical and the connector CON1 toCONn is made possible to be connected to the connecting portion of anyarrangement position so that a minimum number of receiving antennas areused.

As shown in FIG. 32A, the receiving antennas A1 to A4 are arranged atthe positions corresponding to the arrangement positions “1” to “4”where the receiving image would be acquired and the connectors CON1 toCON4 are connected to the corresponding connecting portions.Consequently, the receiving antennas A1 to A4 are set as the intensityreceiving antennas so that a desired receiving image and the receivingfield intensity of each antenna can be obtained by a minimum number ofreceiving antennas and with simple changeover processing.

From the arrangement state shown in FIG. 32A, when the receiving imagescorresponding to other arrangement positions “3” to “6” are to beobtained, aerial portions of the receiving antennas arranged at thearrangement positions “1” and “2” are moved to the portionscorresponding to the arrangement positions “5” and “6” and theconnectors CON1 and CON2 are instead connected to the connectingportions of the connectors CON5 and CON6, respectively (FIG. 32B). Inthis manner, the four receiving antennas can be reused to function asthe six receiving antennas. Also in this case, the number of intensityreceiving antennas is not increased and the changeover processing can beperformed by a minimum number of receiving antennas. Further, the timefor the intensity receiving antenna changeover processing is reduced,thereby rapidly and securely selecting the optimum video receivingantenna. Furthermore, the number of antennas to be mounted on a patientat one time can be reduced, thereby reducing a load on the patient.

Since the connectors CON1 to CONn correspond to the arrangementpositions of the receiving antennas A1 to An in the aforementionedeighth end ninth embodiments, if the connection changes, the changeoverinformation is recorded in correspondence to the receiving image to beused as index information indicating the position of the receivingimage.

Since the antenna can be replaced, the antenna at the positionunnecessary for the receiving is replaced and reused at a positionnecessary for the receiving along with the movement of the capsuleendoscope in the body, thereby obtaining the necessary receiving imageand the antenna receiving field intensity on which the positioncalculation of the capsule endoscope is based by a small number ofantennas.

The structures described in the aforementioned eighth and ninthembodiments are applicable to the aforementioned first to seventhembodiments. In this case, the selection controller C1, C3 to C7 maycontrol as the selection controller C8.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A receiving apparatus for selecting and receiving a radio signal in aframe structure having an information body part including at leastinformation body and an additional part including information forreceiving field intensity measurement by using a plurality of antennas,the apparatus comprising: a controller that measures a receiving fieldintensity of not a first antenna which has received the information bodyin a transmission period of the additional part in a current frame but asecond antenna, and measures a receiving field intensity of the firstantenna in a transmission period of the information body part in thecurrent frame, and if the receiving field intensity of the secondantenna exceeds the receiving field intensity of the first antenna,selects and changes to the second antenna as the first antenna of a nextframe.
 2. The receiving apparatus according to claim 1, wherein when thereceiving field intensity of the second antenna does not exceed thereceiving field intensity of the first antenna, the controllersequentially changes to other second antenna.
 3. The receiving apparatusaccording to claim 1, wherein the controller provides a timing of thereceiving field intensity measurement of the second antenna near thestart of the transmission period of the information body part.
 4. Thereceiving apparatus according to claim 1, wherein the controllermeasures receiving field intensities of a plurality of second antennasin the transmission period of the additional part, and when thereceiving field intensity of a second antenna having the largestreceiving field intensity out of the field intensities of the pluralityof second antennas exceeds the receiving field intensity of the firstantenna, selects and changes to the second antenna as the first antennaof a next frame.
 5. The receiving apparatus according to claim 1,comprising an antenna changeover unit that is connected to each antennain correspondence to arrangement positions of the plurality of antennasand detects a connection state of each antenna to change over theconnected antennas according to an instruction, wherein the controllerselects and changes to an antenna whose connection is detected by theantenna changeover unit.
 6. A receiving apparatus for receiving a radiosignal, transmitted from the inside of a subject, in a frame structurehaving a video signal part for transmitting at least a video signal andan additional part including information for receiving field intensitymeasurement by using a plurality of antennas provided outside thesubject, the apparatus comprising: a changeover unit that selects andchanges over the plurality of antennas; a field intensity measurementunit that measures a receiving field intensity of not a first antennawhich has received the radio signal in a transmission period of theadditional part in a current frame but a second antenna, and measures areceiving field intensity of the first antenna in a transmission periodof the video signal part in the current frame; a selection controllerthat, when the receiving field intensity of the second antenna measuredby the field intensity measurement unit exceeds the receiving fieldintensity of the first antenna, selects the second antenna as the firstantenna of a next frame; and a changeover controller that sequentiallychanges over and connects an antenna other than the first antennaselected by the selection controller in a transmission period of theadditional part of the next frame, and changes to and connects theselected first antenna in a transmission period of the video signalpart.
 7. A receiving apparatus for selecting and receiving a radiosignal in a frame structure having an information body part including atleast information body and an additional part including information forreceiving field intensity measurement by using a plurality of antennas,the apparatus comprising: a controller that measures receiving fieldintensities of more than two antennas in the additional part in acurrent frame, and selects and changes to an antenna having the largestreceiving field intensity out of the more than two antennas as anantenna for receiving the information body part in a current frame. 8.The receiving apparatus according to claim 7, wherein the more than twoantennas are all of the plurality of antennas.
 9. The receivingapparatus according to claim 7, wherein the more than two antennas arean antenna group in which the plurality of antennas are grouped.
 10. Thereceiving apparatus according to claim 7, wherein the more than twoantennas are an antenna group near an antenna which has received theinformation body in a previous frame.
 11. The receiving apparatusaccording to claim 7, wherein the plurality of antennas each have aserial number for a moving path of a transmitting apparatuscommunicating with the receiving apparatus, and the more than twoantennas are an antenna group of the antenna which has received theinformation body in a previous frame and subsequent antennas.
 12. Thereceiving apparatus according to claim 7, comprising an antennachangeover unit that is connected to each antenna in correspondence toarrangement positions of the plurality of antennas and detects aconnection state of each antenna to change over the connected antennasaccording to an instruction, wherein the controller selects and changesto an antenna whose connection has been detected by the antennachangeover unit.
 13. A receiving apparatus for selecting and receiving aradio signal in a frame structure having an information body partincluding at least information body and an additional part includinginformation for receiving field intensity measurement by using aplurality of antennas, the apparatus comprising: a controller thatcompares a first receiving field intensity of an antenna which hasreceived the information body in a previous frame with a secondreceiving field intensity being the largest receiving field intensityout of a result of measurement of receiving field intensities of morethan two antennas other than the antenna in the additional part of acurrent frame, and selects and changes to the antenna having the largerreceiving field intensity as an antenna for receiving the informationbody part in the current frame.
 14. The receiving apparatus according toclaim 13, wherein the more than two antennas are antennas other than theantenna having the first receiving field intensity.
 15. The receivingapparatus according to claim 13, wherein the more than two antennas arean antenna group in which the plurality of antennas are grouped.
 16. Thereceiving apparatus according to claim 13, wherein the more than twoantennas are an antenna group near an antenna which has received theinformation body in a previous frame.
 17. The receiving apparatusaccording to claim 13, wherein the plurality of antennas each have aserial number for a moving path of a transmitting apparatuscommunicating with the receiving apparatus, and the more than twoantennas are an antenna group of the antenna which has received theinformation body in a previous frame and subsequent antennas.
 18. Thereceiving apparatus according to claim 13, comprising an antennachangeover unit that is connected to each antenna in correspondence toarrangement positions of the plurality of antennas and detects aconnection state of each antenna to change over the connected antennasaccording to an instruction, wherein the controller selects and changesto an antenna whose connection has been detected by the antennachangeover unit.
 19. A receiving apparatus for selecting and receiving aradio signal in a frame structure having an information body partincluding at least information body and an additional part includinginformation for receiving field intensity measurement by using aplurality of antennas according to each receiving field intensity,wherein part of a synchronization period of the information body part isset at part or all of a receiving field intensity measurement period ofthe additional part to use a synchronization signal of thesynchronization period as a signal for receiving field intensitymeasurement.
 20. The receiving apparatus according to claim 19,comprising an antenna changeover unit that is connected to each antennain correspondence to arrangement positions of the plurality of antennasand detects a connection state of each antenna to change over theconnected antennas according to an instruction, wherein the controllerselects and changes to an antenna whose connection has been detected bythe antenna changeover unit.
 21. A receiving apparatus for selecting andreceiving a radio signal in a frame structure having an information bodypart including at least information body and an additional partincluding information for receiving field intensity measurement by usinga plurality of antennas according to each receiving field intensity,wherein part of a synchronization period of the information body part isset at part or all of a receiving field intensity measurement period ofthe additional part to use a synchronization signal of thesynchronization period as a signal for receiving field intensitymeasurement, and the antenna for receiving field measurement and theantenna for receiving the information body part are changed over in thesynchronization period according to a measurement result of a receivingfield intensity to each of the plurality of antennas.
 22. The receivingapparatus according to claim 21, wherein the antenna for receiving fieldmeasurement is changed over in the receiving field intensity measurementperiod to measure a receiving field intensity of each antenna.
 23. Thereceiving apparatus according to claim 21, comprising an antennachangeover unit that is connected to each antenna in correspondence toarrangement positions of the plurality of antennas and detects aconnection state of each antenna to change over the connected antennasaccording to an instruction, wherein the controller selects and changesto an antenna whose connection has been detected by the antennachangeover unit.
 24. A receiving apparatus for receiving a radio signalin a frame structure having an information body part including at leastinformation body as a radio signal transmitted from a movingtransmitting apparatus and an additional part including information forreceiving field intensity measurement, the receiving apparatuscomprising: an antenna changeover unit that is connected to each antennain correspondence to arrangement positions of the plurality of antennasand detects a connection state of each antenna to change over theconnected antennas according to an instruction, and a controller thatsequentially changes to an antenna whose connection has been detected bythe antenna changeover unit on reception of the additional part todetect a receiving field intensity, and changes to an antenna having thelargest receiving field intensity to cause the antenna to receive aradio signal of the information body part.
 25. The receiving apparatusaccording to claim 24, wherein a number of the plurality of antennas isless than a number of the plurality of connecting portions, and theplurality of antennas are used by replacing part of a plurality ofalready connected antennas with other connecting portions.
 26. Thereceiving apparatus according to claim 24, wherein the controllermeasures receiving field intensities of a plurality of antennas in areceiving period of the additional part.